Organic electro-luminescence diode

ABSTRACT

An organic electro-luminescence diode comprises two electrodes and an organic electro-luminescence structure. The organic electro-luminescence structure is formed between the two electrodes, and includes a red light-generating unit, a green light-generating unit, a blue light-generating unit and a light-compensating unit stacked with each other. The light-compensating unit is selected from the group consisting of a white light-compensating unit, a red light-compensating unit, a green light-compensating unit, a blue light-compensating unit and a structure stacking together one light-compensating unit upon the other.

This application is a divisional application of U.S. patent applicationSer. No. 11/284,013 filed on Nov. 22, 2005, which claims the benefits ofTaiwan Application No. 94104786, filed Feb. 18, 2005, the contents ofwhich are herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to an organic electro-luminescence diode,especially to an organic light-emitting diode having serially stackedred, green, and blue light-generating units.

(2) Description of the Related Art

Two ways for conventional multicolor organic light-emitting diode (OLED)to generate three primary color light are that arranging red (R). green(G), and blue (B) light-generating units side by side, and combining awhite light-generating unit with color filters. However, side by sidepatterns used in a manufacturing process of a flat panel will causeshadow effect. The shadow effect can be avoided by the other way such ascombining the white light-generating unit with color filters, but thecolor filters may reduce the light intensity.

FIG. 1A shows a first type of conventional OLED panel with side by sidepatterns. R, G, and B light-generating units 20 are disposed side byside on a substrate 10. Each light-generating unit includes a holeinjecting layer (HIL) 22, a hole transport layer (HTL) 23, an emissionlayer (EL) 24, an electron transport layer (ETL) 25 and an electroninjecting layer (EIL) 26 sandwiched between two electrodes 21 a and 21b. First of all, the electrode 21 b used as an anode is formed on thesubstrate 10. Subsequently, the HIL 22, the HTL 23, the EL 24, the ETL25 and the EIL 26 are formed on the electrode 21 b in order. Finally,the electrode 21 a is formed on the EIL 26 as a cathode. Referring toFIG. 1B, when different color ELs 24 are evaporated on the substrate 10,they are aligned for deposited on accuracy site by adjusting evaporatingangle .theta. The different evaporating angle .theta. causes ELs 24evaporated non-uniformly in overall panel, and results in shadow effect.

FIG. 1C shows a second type of conventional OLED having a whitelight-generating unit with color filters. A red color filter layer 11, agreen color filter layer 12 and a blue color filter layer 13 are formedon the substrate 10, and a white light-generating unit 20 a is locatedon the three color filter layers 11, 12, and 13. As described in U.S.Pat. No. 6,696,177, the light-generating unit 20 a can produce whitelight by a blue emission layer 201 containing an yellow fluorescencematerial. Because the light-generating units 20 a in this type of OLEDare not disposed side by side, the shadow effect does not occur.However, the luminance will be reduce due to the light going through thecolor filters 11, 12, and 13. Because different color lights havedifferent luminance attenuation ratio, the luminescent efficiency of theblue light-generating unit and that of the red light-generating unit areusually lower than that of the green light.

In order to improve the disadvantages of forgoing two type of OLED, theinventor provides an OLED having serially stacked RGB light-generatingunits.

SUMMARY OF THE INVENTION

Accordingly, the object of the invention is to provide an OLED forhigher light intensity, higher luminescent efficiency and purer whitelight by serially stacked red, green, blue and additional whitelight-generating units, any one of which includes an emission layersandwiched between a hole injecting/transport layer and an electroninjecting/transport layer.

The present invention provides an organic light-emitting diodecomprising two electrodes and an organic electro-luminescence structure.The organic electro-luminescence structure is sandwiched between the twoelectrodes, and includes a red light-generating unit, a greenlight-generating unit, a blue light-generating unit and alight-compensating unit stacked with each other. The light-compensatingunit is selected from the group consisting of a white light-compensatingunit, a red light-compensating unit, a green light-compensating unit, ablue light-compensating unit and combinations thereof.

Besides, a charge generating layer is interposed between any twoadjacent light-generating units or between one light-compensating unitand its adjacent light-generating unit. When the light-compensating unitincludes a series of the white light-compensating units, the redlight-compensating units, the green light-compensating units, the bluelight-compensating units or their combinations, the charger generatinglayers can be also interposed between any two adjacentlight-compensating units.

When the white light-compensating unit is added, the luminescentefficiency of the OLED is improved to emit more saturated red, green andblue light. If the red light-compensating unit or the bluelight-compensating unit are added, the intensity of the red and bluelight emitting from the OLED is sufficient to balance with green light,so as to generate purer white light. Thus, the OLED device should bebright, efficient, and generally have Commission International del'Eclairage (CIE) chromaticity coordinates of about [0.33, 0.33].

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be specified with reference to itspreferred embodiment illustrated in the drawings, in which

FIG. 1A is a chart showing the convention OLED panel having RGBlight-generating units disposed side by side;

FIG. 1B is a chart showing the evaporating process of the OLED in FIG.1A;

FIG. 1C is a chart showing the convention OLED panel having a whitelight-generating unit with color filters;

FIG. 2 is a chart showing the OLED according to the invention;

FIG. 3 is a chart showing a first embodiment of the OLED according tothe invention;

FIG. 4 is a chart showing a second embodiment of the OLED according tothe invention;

FIG. 5 is a chart showing a third embodiment of the OLED according tothe invention;

FIG. 6 is a chart showing a fourth embodiment of the OLED according tothe invention;

FIG. 7 is a chart showing a fifth embodiment of the OLED according tothe invention;

FIG. 8 is a chart showing a sixth embodiment of the OLED according tothe invention; and

FIG. 9 is a chart showing a seventh embodiment of the OLED according tothe invention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 2, the organic light-emitting diode 30 according tothe invention comprises two electrodes 31 and 32 and an organicelectro-luminescence structure 301. The organic electro-luminescencestructure 301 is sandwiched between two electrodes 31 and 32, andincludes a red light-generating unit 35, a green light-generating unit34, a blue light-generating unit 33 and a light-compensating unit 36,all of which are stacked with each other.

As shown in FIG. 2, the blue light-generating unit 33 is formed on theelectrode 31 and combined with the green light-generating unit 34through a charge generating layer 37. Likewise, the greenlight-generating unit 34 is combined with the red light-generating unit35 through the charge generating layer 37. The red light-generating unit35 is still combined with the light-compensating unit 36 through thecharge generating layer 37. Besides, the OLED 30 of the presentinvention may include a white light-generating unit (not shown) that isselectively stacked with any other light-generating units 33, 34 and 35and the light-compensating unit 36. On top of the light-compensatingunit 36 is the other electrode 32. These light-generating units or thelight-compensating unit can be made up of a hole injecting layer, a holetransport layer, an emission layer, an electron transport layer and anelectron injecting layer. For example, the light-compensating unit 36has a hole injecting/transport layer 361, an emission layer 362 and anelectron injecting/transport layer 363. The difference between thisinvention and related art is that all units in the organicelectron-luminescence structure 301 are stacked with each other, and thelight-compensating unit 36 is added in this invention. Specially, thelight-compensating unit 36 is selected from a group consisting of awhite light-compensating unit, a red light-compensating unit, a greenlight-compensating unit, a blue light-compensating unit and combinationsthereof. In addition, the stacking order for these light-generatingunits and the light-compensating unit is not necessary to limit.

Referring to FIG. 3, the first preferred embodiment of this invention isshown. A red color filter layer 43, a green color filter layer 44, ablue color filter layer 45 and a transparent layer 46 are deposited sideby side on a substrate 42. An OLED 40 is on these layers 43, 44, 45 and46. In order to enhance the light intensity, the luminescent efficiencyand the saturation, the white light-compensating unit 41 is selected toeliminate the color shift. As shown, an organic electro-luminescencestructure 401 is constituted of the white light-compensating unit 41,the red light-generating unit 35, the green light-generating unit 34 andthe blue light-generating unit 33. These charge generating layers 37should be interposed between any two adjacent light-generating units orbetween white light-compensating unit 41 and its adjacentlight-generating unit, such as the red light-generating unit 35. Thecharge generating layer 37 has the function of conducting current byholes and electrons generating from an oxidation/reduction reaction.

Referring to FIG. 4, the second preferred embodiment of this inventionis shown. When the white light that is generated by mixing the lightsemitting from the red light-generating unit 35, the greenlight-generating unit 34 and the blue light-generating unit 33 shifts toblue-green, a red light-compensating unit 51 is selected to eliminatethe color shift. So an organic electro-luminescence structure 501 isconstituted of the red light-compensating unit 51, the redlight-generating unit 35, the green light-generating unit 34 and theblue light-generating unit 33. These charge generating layers 37 shouldbe interposed between any two adjacent light-generating units or betweenthe red light-compensating unit 51 and its adjacent light-generatingunit. The most suitable position of the red light-compensating unit 51is adjacent to the red light-generating unit 35.

Referring to FIG. 5, the third preferred embodiment of this invention isshown. When the white light shifts to red, a blue light-compensatingunit 61 is selected to eliminate the color shift. So an organicelectro-luminescence structure 601 is constituted of the bluelight-compensating unit 61, the red light-generating unit 35, the greenlight-generating unit 34 and the blue light-generating unit 33. Thesecharge generating layers 37 should be interposed between any twoadjacent light-generating units or between the blue light-compensatingunit 61 and its adjacent light-generating unit. The most suitableposition of the blue light-compensating unit 61 is adjacent to the bluelight-generating unit 33.

FIG. 2 to FIG. 5 explain that if the color shift is not serious, onlyone mono-color light-compensating unit is sufficient to eliminate thecolor shift by adjusting the red, green and blue light in an intensityratio of from 1:1:1 to 1:2:1.

Referring to FIG. 6, the fourth preferred embodiment of this inventionis shown. When the white light shifts to blue-green, a redlight-compensating unit 71 is selected to eliminate the color shift.However, if only one red light-compensating unit 71 can not balance theintensity of red, green and blue light, other red light-compensatingunits 71 will be added in the OLED 70. As shown, there are two redlight-compensating unit 71, one red light-generating unit 35, one greenlight-generating unit 34 and one blue light-generating unit 33sandwiched between a pair of electrode 31 and 32. These chargegenerating layers 37 are interposed between two red light-compensatingunits 71, between any two adjacent light-generating units or between onered light-compensating unit 71 and its adjacent light-generating unit.The most suitable position of the red light-compensating unit 71 isadjacent to the red light-generating unit 35. Two to four redlight-compensating units 71 are suitable in this embodiment. In otherwords, an organic electro-luminescence structure 701 has two to fourserial red emission layers to compensate the luminance and thesaturation of the red light.

Referring to FIG. 7, the fifth preferred embodiment of this invention isshown. When the white light shifts to red, a blue light-compensatingunit 81 is selected to eliminate the color shift. As shown, there are aplurality of blue light-compensating unit 81, one red light-generatingunit 35, one green light-generating unit 34 and one bluelight-generating unit 33 sandwiched between a pair of electrode 31 and32. These charge generating layers 37 are interposed between any twoblue light-compensating units 81, between any two adjacentlight-generating units, or between one of the blue light-compensatingunits 81 and its adjacent light-generating unit. The most suitableposition of the blue light-compensating unit 81 is adjacent to the bluelight-generating unit 33. Two to four blue light-compensating units 81are adapted to this embodiment for example. In other words, the organicelectro-luminescence structure 801 has two to four serial red emissionlayers to compensate the luminance and the saturation of the blue light.

FIG. 6-7 are different from FIG. 2-5 because of a plurality ofmono-color light-compensating units for adjusting the red, green andblue light in an intensity ratio of from 1:1:1 to 1:2:1. The numberrequirement of the light-compensating units varies with the factors suchas different electrode materials, different hole injecting/transportlayer materials, different electron injecting/transport layer materialsor emission layers, because the different materials give rise todeviation of the light intensity.

Referring to FIG. 8, the sixth preferred embodiment of this invention isshown. When the white light shifts to green, a blue light-compensatingunit 91 and a red light-compensating unit 92 are selected to eliminatethe color shift. There are a plurality of blue light-compensating units91, one red light-generating unit 35, one green light-generating unit34, one blue light-generating unit 33 and a plurality of redlight-compensating units 92 sandwiched between two electrode 31 and 32.These charge generating layers 37 are interposed between any twoadjacent blue light-compensating units 91, between any two adjacent redlight-compensating units 92, between any two adjacent light-generatingunits or between one light-compensating unit and its adjacentlight-generating unit. The most suitable position of the bluelight-compensating unit 91 is adjacent to the blue light-generating unit33, and the most suitable position of the red light-compensating unit 92is adjacent to the red light-generating unit 35. Two to four bluelight-compensating units 91 or two to four red light-compensating units92 are adapted to this embodiment. Therefore, an organicelectro-luminescence 901 has two to four serial red emission layers ortwo to four serial blue emission layers.

Referring to FIG. 9, the seventh preferred embodiment of this inventionis shown. When the intensity of the light from the red, green and bluelight-generating units are not sufficient, the white light-generatingunit 101 or the white light-compensating unit 41 are, added selectivelyto enhance the light intensity and saturation. There are one whitelight-generating unit 101, one red light-generating unit 35, one greenlight-generating unit 34, one blue light-generating unit 33 and aplurality of white light-compensating units 41 between two electrode 31and 32. These charge generating layers 37 are interposed between any twoadjacent white light-compensating units 41, between any two adjacentlight-generating units or between one light-compensating unit and itsadjacent light-generating unit. The most suitable position of the whitelight-compensating unit 41 is adjacent to the white light-generatingunit 101. Two to four white light-compensating units 41 are adapted tothis embodiment. Therefore, an organic electro-luminescence structure1001 has two to four serial white emission layers.

By the way, the red light-generating unit, the green light-generatingunit and the blue light-generating unit can be stacked in any order inaforementioned embodiments. These color filter layers can be formedbetween the OLED and the substrate, or the surface of the substrateopposite to the OLED. The OLED emits red, green and blue light in a bestlight intensity ratio of 1:2:1. The red light-generating unit and thered light-compensating unit can be made from the same or differentmaterials. The blue light-generating unit and the bluelight-compensating unit can be made from the same or differentmaterials. The blue light-generating unit and the bluelight-compensating unit can be made from the same or differentmaterials.

The present invention also provides a method for manufacturing an OLEDaccording to the invention comprising the steps of: providing a firstelectrode; forming and serially stacking a plurality of light-generatingunits, at least one light-compensating unit and at least one chargegenerating layer on the first electrode, wherein the charge generatinglayer is disposed between these light-generating units; and forming asecond electrode on the light-compensating unit, these light-generatingunits and these charge generating layers. The light-generating units caninclude one red light-generating unit, one green light-generating unit,one blue light-generating unit and one white light-generating unit.

If the organic electro-luminescence structure has a plurality of redlight-compensating units, the steps of forming the light-compensatingunit further include a step of forming a plurality of red emissionlayers, for example, two to four red emission layers are suitable. Ifthe organic electro-luminescence structure has a plurality of bluelight-compensating units, the steps of forming the light-compensatingunit further include a step of forming a plurality of blue emissionlayers, for example, two to four blue emission layers are suitable. Theorganic layers in the light-generating units or the light-compensatingunits, such as the hole injecting layer, the hole transport layer, theemission layer, the electron transport layer and the electron injectinglayer can be deposited by evaporating. The electron injecting layer canbe doped with n-dopant to increase the number of electrons, and the holeinjecting layer can be doped with p-dopant to increase the number ofholes. The electrodes can be made by evaporating or sputtering forexample.

Characteristics and advantages of the invention are listed: [0039] 1.Enhancing the luminescent efficiency and balancing the green light toproduce purer white light. [0040] 2. Longer life for the OLED. [0041] 3.Compensating luminance attenuation. [0042] 4. No alignment inevaporating process, and no shadow effect.

While the preferred embodiments of the present invention have been setforth for the purpose of disclosure, modifications of the disclosedembodiments of the present invention as well as other embodimentsthereof may occur to those skilled in the art. Accordingly, the appendedclaims are intended to cover all embodiments which do not depart fromthe spirit and scope of the present invention.

The invention claimed is:
 1. An organic electro-luminescence diodecomprising: a substrate; a transparent layer disposed on the substrate;two electrodes disposed on the transparent layer; and an organicelectro-luminescence structure disposed between said two electrodes,consisting: a red light-generating unit; a green light-generating unit;a blue light-generating unit, wherein said three light-generating unitsare stacked with each other; a light-compensating unit stacked with saidlight-generating units, wherein the light-compensating unit only emitsone color, and the one color comprises a primary color; and severalcharge generating layers, wherein between each two of thelight-generating units and the light-compensating unit is disposed withone said charge generating layer.
 2. The organic electro-luminescencediode of claim 1, wherein said light-compensating unit emits red color.3. The organic electro-luminescence diode of claim 1, wherein saidlight-compensating unit emits green color.
 4. The organicelectro-luminescence diode of claim 1, wherein said light-compensatingunit emits blue color.
 5. The organic electro-luminescence diode ofclaim 1, wherein the light intensity ratio of red light:green light:bluelight is about from 1:1:1 to 1:2:1.
 6. The organic electro-luminescencediode of claim 1, wherein said red light-generating unit and saidlight-compensating unit have the same materials.
 7. The organicelectro-luminescence diode of claim 1, wherein said greenlight-generating unit and said light-compensating unit have the samematerials.
 8. The organic electro-luminescence diode of claim 1, whereinsaid blue light-generating unit and said light-compensating unit havethe same materials.
 9. The organic electro-luminescence diode of claim1, further including a white light-generating unit stacked with saidorganic electro-luminescence structure between said two electrodes. 10.A method for manufacturing an organic electro-luminescence diode,comprising: providing a substrate; forming a transparent layer on thesubstrate; forming a first electrode on the transparent layer; formingan organic electro-luminescence structure, wherein the organicelectro-luminescence structure consists of a red light-generating unit,a green light-generating unit, a blue light-generating unit, alight-compensating unit and several charge generating layers, whereinthe light-compensating unit only emits one color and the one colorcomprises a primary color, and the three light-generating units and thelight-compensating unit are stacked serially, and between each two ofthe light-generating units and the light-compensating unit is disposedwith one the charge generating layer; and forming a second electrode onsaid organic electro-luminescence structure.
 11. The method of claim 10,wherein the light-compensating unit emits red color.
 12. The method ofclaim 10, wherein the light-compensating unit emits green color.
 13. Themethod of claim 10, wherein the light-compensating unit emits bluecolor.
 14. An organic electro-luminescence diode comprising: asubstrate; a transparent layer disposed on the substrate; two electrodesdisposed on the transparent layer; and an organic electro-luminescencestructure disposed between said two electrodes, comprising: a redlight-generating unit; a green light-generating unit; a bluelight-generating unit, wherein said three light-generating units arestacked with each other; a plurality of charge generating layersdisposed between said two electrodes; and a red light-compensating unit,wherein one of the charge generating layers is disposed between andcontacts the red light-compensating unit and the red light-generatingunit.
 15. The organic electro-luminescence diode of claim 14, whereinsaid red light-generating unit and said red light-compensating unit havethe same materials.
 16. The organic electro-luminescence diode of claim14, further including a white light-generating unit stacked with saidorganic electro-luminescence structure between said two electrodes.